The present invention relates to electron beam devices and more particularly to such devices utilizing magnetic collimiation of the electron beam trajectories.
A wide variety of devices have been proposed for reducing the depth of conventional cathode ray tubes. One of the conventional approaches has a single electron gun mounted on the side of the tube in a non-perpendicular relationship to a cathodoluminescent screen. The electron beam generated by the gun initially has a trajectory which is substantially parallel to the screen and at some point in its travel, the beam gets bent sharply toward the screen so that it will impinge thereupon. One of the problems encountered in all of these types of devices is to accurately control the beam trajectory so as to scan a conventional raster such as that utilized in the NTSC, PAL and SECAM television systems. The tendency of the beam trajectory in many of these devices is to scan an arc rather than a straight line producing a picture which has a keystone shape. Another common problem is large variations in spot size at different points on the cathodoluminescent screen due to variation in the angle of incidence at which the electron beam strikes the screen at these different points.